textproduct: Rapid City

KEY MESSAGES

- Slight risk (level 2 of 5) over western SD for today with main threats including large to very large hail (2+") and damaging winds (70+ mph). There is also a very low risk for tornadoes.

- Slight risk (level 2 of 5) over western SD for Friday with main threats including large to very large hail (2+") and damaging winds (60+ mph).

- Marginal risk (level 1 of 5) over the Black Hills for Saturday with main threats including large hail (1+") and damaging winds (60+ mph).

DISCUSSION

(This Afternoon Through Wednesday) Issued at 1154 AM MDT Thu Jul 2 2026

Bottom line up front: There will be daily chances for thunderstorms, some strong to severe with large to very large hail and damaging wind gusts as primary hazards, through much of the holiday weekend.

Upper level analysis depicts trough over the western US. A subtle shortwave feature is apparent over UT/ID in water vapor imagery. A layer of wildfire smoke aloft is resulting in hazy skies over the Northern Plains. Closer to home, isolated convection associated with another weak wave has developed this morning across northeastern WY into western SD. This convection should clear out by the afternoon, no severe weather is expected with this round of storms.

This Afternoon/Evening: Attention turns to this afternoon where scattered strong to severe thunderstorms are possible. There is some question as to how the convection this morning, the wildfire smoke aloft, and subtle 500mb height rises will impact storm chances later this afternoon and evening. Short range model guidance depicts around 2000-3000 J/kg CAPE over northwestern into south central SD by this afternoon. Deep layer shear of 30-40kt will support organized convection and multicells in any storms that do form. CAMs from this morning show storms developing off the higher terrain of the northern Black Hills into northwestern SD where the greatest instability is. These storms will have the highest likelihood of becoming severe with large to very large hail and damaging wind gusts as the main hazards. Dry air near the surface will limit overall tornado potential, but an isolated tornado or two can't be ruled out. As for timing, discrete storms will begin to develop along the SD/MT border and the northern Black Hills as early as 1 pm and move eastward and grow into an MCS through the afternoon and evening. If convection develops far enough south, the storms may reach the Rapid City area by around 5 or 6 pm.

Friday: A stronger wave approaches the area Friday with a risk for scattered severe storms. The 12z NAM has 2000-3000 J/kg CAPE developing over the Black Hills into southwestern and south central SD by mid afternoon Friday. Meanwhile, increasing mid- level flow will contribute to 30-40kt effective shear developing over the area. This should be enough to support supercell development with large to very large hail and damaging winds as the main threats. There's still some uncertainty as to how the storms will evolve with any outflows from today's convection influencing development tomorrow.

Saturday: Unsettled flow continues through Saturday with shortwave ridging developing to our west. The ridge will limit overall storm chances. However, moderate instability (2000-2500 J/kg CAPE per the NAM) will develop over the Black Hills by Saturday afternoon with 30- 40KT bulk shear. Storms may develop over the higher terrain of the Black Hills before moving eastward into the adjacent plains. There's enough shear and instability to support marginal severe potential with large hail and damaging winds as the main hazards.

By Sunday, the upper ridge will have moved overhead and this should keep things dry through the end of the weekend. Along with the ridge, temperatures will warm up slightly to the upper 80s to upper 90s. Hot weather with daily chances for storms will continue through early next week with highs in the upper 80s to 90s.

AVIATION

(For the 18Z TAFS Through 18Z Friday) Issued At 1143 AM MDT Thu Jul 2 2026

VFR conditions are mainly expected throughout the forecast period.

Aviation concerns are centered around the isolated to scattered thunderstorms initiating over the northern Black Hills region between 19-21z this afternoon. Storms will track east to northeastward. Some storms may be severe with gusty winds and large hail. Can't rule out the isolated tornado threat.

MVFR conditions likely underneath storm cores, but confidence on if and when a core may impact a given terminal is low. Have maintained a PROB30 for KRAP with an earlier start time based on the latest high-res guidance/CAMs.

A lull may occur right after sunset, but some guidance suggests additional overnight convection is possible into early Friday morning, with low confidence on timing and location.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.